General Description of Arcing in Air and Solid Materials:
Arcing can occur as a result of electrical wire damage. For example, a nail or a screw may puncture insulation or create a small break in a conductor. As a result, an arc can form, and traverse air or punch through compromised insulation. While all arcs are generally formed in similar ways, the electrical characteristics of arcing through air can be different from those of arcing through carbonized insulation.
An arc is an accelerated electron phenomenon. As an electric field increases, for example due to increasing voltage, electrons typically begin to move along the electric field, skipping from one atom to another. In a solid material, an electron flow over a finite amount of time can be considered a current. This current may be seen as an arc. Yet, when electrons are stripped from atoms at one end of a solid material, higher electric field strength is typically required to strip an additional electron. The arc path can as a result become unsuitable for sustaining an arc, forcing the arc to find another path. Over time, a used path can eventually recover, though several other arc paths may be used before a path or a portion of a path regains its suitability. In air, a similar phenomenon may occur. Yet, the movement of air can create additional features of a discharge. For example, “previous path” may not exist in the context of an arc in air, because of the movement of air. Furthermore, even when air is highly confined, it can be heated during arcing, resulting in substantial turbulence within the space.
Arcs in a solid material tend to break molecular bonds. They can encourage new bonds and new chemical composition in the solid material. In most plastics, for example, an arc can dissociate carbon from hydrogen. As hydrogen escapes into air, carbon is left in the plastic, usually with a black appearance, in a process often referred to as carbonization. Since carbon is more conductive than most plastics, areas of carbonization tend to be locations where arcing often recurs. These areas are usually in the form of small black pits, rather than large areas of carbon, which can nevertheless occur in extreme cases.
Although devices exist for detecting arcing in electrical circuits, they typically face such problems as oversensitive arcing detection or erroneous arcing identification. For example, conventional arc fault circuit interrupters often trip when detecting arcing due to the normal functioning of electrical components such as electric motors, rather than when detecting arcing due to electrical wire damage. Therefore, there is a need for a system that allows for more accurate detection and identification of potentially unwanted arcing with speed and accuracy appropriate for commercial applications.